The zebrafish, Danio rerio, has become an increasingly popular model system for studying vertebrate development. Its high fecundity and the ease with which large numbers of individuals can be bred and maintained make it a very suitable system for genetic analysis. The transparency of the zebrafish embryo and its accessibility to a variety of embryological manipulations offer a unique combination of genetics and embryology for studying vertebrate development. Large scale genetic screens have identified more than 600 genes with unique and essential functions during zebrafish development. Many of these genes are likely to be relevant to human development and disease. The major next step in the analysis of these genes is the molecular cloning of the genes disrupted by these mutations. Towards this aim, the investigators are systematically mapping these mutations using microsatellite markers. To date, more than 140 mutations have been placed on the genetic map. In an effort to identify potential candidate genes that may be affected by these mutations, they have generated a zebrafish radiation hybrid map of 1383 markers consisting of 941 SSLPs, 278 cDNAs and 164 ESTs. This map is currently the most comprehensive radiation hybrid map of any model organism. The aim of this proposal is to integrate an additional 5,000 markers into the zebrafish radiation hybrid map. One of the goals is to increase the continuity and coverage of the RH map by adding SSLP markers that are genetically mapped. Another goal is to increase the density of the RH map by integrating a large number of ESTs into the RH map. The integration of the RH map with the existing genetic map will be extremely valuable for identifying linkages between mutations and potential candidate genes. The investigators will use their established and streamlined approach for performing and analyzing the large number of PCR reactions involved in generating a RH map. Their experience with high-throughput PCR, computer-assisted gel imaging and semi-automated data analysis will allow them to generate an RH map of the zebrafish genome efficiently and in a cost-effective way. The availability of an RH map will be one of the key components for efficient cloning of the genes that have been identified by mutations in the zebrafish.